The concentration of copper in the vitreous body of the eye which contains a foreign body is to be measured by a recently developed method employing X-ray fluorescence. This permits to determine whether the foreign body contains copper which started to dissolve, in which case extraction of the foreign body might be imperative. The degree of dissolution shall be compared with other clinical parameters, foremost ERG. Animal experiments shall be conducted on the relation of copper concentration in vivo and variations in the ERG with ultimate histological examination of the various parts of the eye as to deformations and copper deposition with simultaneous measurement of the copper concentration at these sites.